1. Field of the Invention
This invention relates to X-ray spectroscopes used for spectral detection of characteristic X-rays, particularly ultra soft X-rays such as those from beryllium, boron, carbon, nitrogen and oxygen.
2. Description of the Prior Art
In the fluorescence X-ray spectrometry, detection of a substance generating ultra soft X-rays such as carbon is very difficult and requires particularly high efficiency means of the analysis because of very low efficiency of X-ray generation, usually about 0.05% at most and also high absorption of the X-rays by the substance. The spectroscopes employed hitherto have used multi-layer films of metal salt of higher fatty acid or concave diffraction gratings as mentioned in "Advances in X-Ray Analysis", Vol. 7, page 497 (1967). Their reflectivity, however, has been low, no higher than several percent, so that quantitative analysis in case with concentration of no higher than several percent such as the measurement of the carbon in iron and steel has been practically impossible.